Tapered thread configuration with improved durability

ABSTRACT

Underground drilling operation often requires connecting a drill tool (e.g., drill bit, backreamer, etc.) to a drill string. It is desirable to connect the drill tools to a drill string in a manner that facilitates quick and easy assembly and disassembly. Low torque coupling, commonly referred to as “torque-less” connection, can provide such functionality. The useful life and strength of such connections can be improved upon. The present disclosure provides a low torque coupling with improved strength and durability.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/380,168 filed on Jun. 26, 2012, which is a National Stage Applicationof PCT/US2011/062356 filed on Nov. 29, 2011, which claims priority toU.S. Provisional Patent Application Ser. No. 61/418,783, filed Dec. 1,2010 and U.S. Provisional Patent Application Ser. No. 61/435,689, filedJan. 24, 2011, which applications are incorporated herein by referencein their entirety.

TECHNICAL FIELD

The present disclosure provides a coupling for connecting a drill toolto a drill string and related methods.

BACKGROUND

Underground drilling operation often requires connecting a drill tool(e.g., drill bit, backreamer, etc.) to a drill string. It is desirableto connect the drill tools to a drill string in a manner thatfacilitates quick and easy assembly and disassembly. Low torquecoupling, commonly referred to as “torque-less” connection, can providesuch functionality. The useful life and strength of such connections canbe improved upon. The present disclosure provides a low torque couplingwith improved strength and durability.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic illustration of a drilling machine in operation;

FIG. 2 is a perspective view of a coupling according to the principlesof the present disclosure;

FIG. 3 is a cross-sectional view of a portion of the coupling of FIG. 2;

FIG. 4 is a cross-sectional view of an alternative embodiment of thecoupling shown in FIG. 3;

FIG. 5 is a side view of a portion of the coupling of FIG. 2 shown in afully engaged position;

FIG. 6 is a cross-sectional view along line 6-6 of FIG. 5;

FIG. 7 is an enlarged view of a portion of FIG. 6 labeled 7;

FIG. 8 is an enlarged view of a portion of FIG. 6 labeled 8;

FIG. 9 is a view of the subject matter of FIG. 7 with the coupling shownin a partially engaged position;

FIG. 10 is a cross-sectional view of an alternative embodiment of thecoupling of FIG. 2;

FIG. 11 is a cross-sectional view of an alternative embodiment of thecoupling of FIG. 2;

FIG. 12 is a mass-sectional view of the coupling of FIG. 11 along lines12-12;

FIG. 13 is a side view of a portion of the coupling of FIG. 11; and

FIG. 14 is a side view of an alternative embodiment of the portion ofthe coupling shown in FIG. 13.

DETAILED DESCRIPTION

Referring to FIG. 1 a drilling machine 10 is shown driving a drillstring 20 into the ground. The distal end of the drill string includes adrill tool assembly 100. The coupling between an end of the drill string20 and the drill tool assembly 100 is shown in greater detail in FIGS.2-9.

Referring generally to FIGS. 2-9, a coupling between a starter rod 12and a sonde housing 14 is shown. The starter rod 12, also referred to asa pilot rod or generically a first member, is threadly connected to thedistal most (down hole most) drill rod 16 via a torque connection. Thesonde housing 14 is configured to house a sonde therein and supports adrill bit (not shown) at its distal end 24.

In the depicted embodiment an adaptor 18 is threadly connected in theproximal end 22 of the sonde housing 14 via a torque connection. Theadaptor 18 and sonde 14 are also referred to herein generically as asecond member. A collar 26 is provided to slide over a distal end 28 ofthe starter rod 12 and a portion of the adaptor 18 to prevent relativerotation between the starter rod and adaptor (and hence also preventrelative rotation between the starter rod 12 and the sonde housing 14).

In the depicted embodiment an inner surface of the collar 26 isconfigured to engage external structural features on the distal end 28of the starter rod 12 and on the exterior surface of the adaptor 18. Inthe depicted embodiment the collar includes internal flats 30 thatengage flats 32 on the distal end 28 of the starter rod 12 and flats 68on the exterior of the adaptor 18. The connection between the distal end28 of the starter rod 12 and the proximal end 36 of the adapter 18 isdescribed in greater detail below.

In the depicted embodiment the coupling includes first member includinga driving end and a driven end. In the depicted embodiment, the firstmember is shown as the starter rod 12. The drive end is shown as thedistal end 28 and the driven end is shown as the proximal end 34. Theproximal end 34 is threadly connected to the down hole most drill rod 16via a torque connection.

In the depicted embodiment the driving end of a first member (e.g., thedistal end 28 of the starter rod 12) includes a tapered portion (recess36 shown in FIG. 3 or protrusion 38 shown in FIG. 4) including threadsthereon. The driving end includes a first land 40 (FIG. 6) adjacent adistal end of the tapered portion (e.g., the protrusion 38 or recess 36and a second land 42 (FIG. 6 adjacent a proximal end of the taperedportions (protrusion 38 or recess 36).

In the depicted embodiment the second member (adaptor 18) includes adrive end 44 and a driven end 46. The drive end 44 includes a threadedconnection for attaching to a cutting tool (e.g., a sonde housing 14supporting a drill bit). The driven end 46 is adapted for connectionwith the driving end 28 of the first member 12. The driven end 46includes a tapered portion (e.g., recess 48 shown in FIG. 4 orprotrusion 50 shown in FIG. 6) including threads thereon. The driven end46 includes a third land portion 52 (FIG. 6) adjacent a distal end ofthe tapered portion (e.g., recess 48 or protrusion 50). The drive end 46also includes a fourth land portion 54 adjacent a proximal end of thetapered portion.

In the depicted embodiment the first land 40 is configured to engage thefourth land 54 and the second land 42 is configured to engage the thirdland 52 when the tapered threads on the first member 28 are engaged withthe tapered threads on the second member 18. In the depicted embodimentthe clearance between the first land 40 and fourth land 54 and theclearance between the second land 42 and the third land 52 is sufficientto allow a user to slidably engage the first and second members by hand.In the depicted embodiment the first land and the fourth land arecylindrical having diameters that are at least 0.003 inches differentfrom each other (for example, within 0.003 inches to 0.006 inches (0.076to 0.150 millimeters) of each other). In other words, the clearancebetween the surfaces of the lands in a radial direction (radialclearance) is between 0.0015 to 0.003 inches (0.038 to 0.076millimeters). It should be appreciated that in alternative embodimentthe lands could be of different geometric configurations and havedifferent clearance therebetween.

In some embodiment the peaks 58 of the threads on the tapered portion ofsecond member and valleys 60 of the threads of the first member areoffset by at least 0.030 inches (0.76 millimeters) even when the threadsare engaged. In the depicted embodiment the pitch diameter between thethreaded portions on the first and second members are offset by at least0.030 inches. On a tapered thread like the ones shown the pitch diameterat a given position on the thread axis is the diameter of the pitch coneat that position. It should be appreciated that when the crest of thethread is truncated beyond the pitch line, the pitch diameter and pitchcylinder or pitch cone would be based on theoretical extension of thethreaded flanks.

As discussed above, the second member is depicted as an adapter 18.However, it should be appreciated that in alternative embodiments thefirst member can be different components including, for example, a drillbit or a sonde housing.

In the depicted embodiment the threads on the tapered recess and threadsof the tapered protrusions are asymmetric having a tooth width W toheight H ratio between 1.25 to 3.0 (FIG. 9). The asymmetric shortthreads facilitate self-alignment and maintain the above-describedoffset between peaks and valleys of corresponding threads.

In the depicted embodiment the first member 28 includes structure thatabuts structure on the second member 18 to limit the offset between thepeaks of the threads on the tapered recess and valleys of the threads ofthe tapered protrusions. The structure on the first member is shown asfront face 62 and the structure on the second member is shown as anannular shoulder 64.

In the depicted embodiment, a portion 66 (FIG. 8) of the tapered recessat its distal end is enlarged and does not include threads thereon. Inthe depicted embodiment, a portion of the tapered recess at its proximalend is also enlarged (portion 67 of FIG. 7) and does not include threadsthereon. These portions are configured to receive foreign matter (e.g.,rock and dirt) and thereby prevent the matter from jamming theconnection between the first and second members, in addition, theseportions also act as stress relief zones that distribute load at thetransition, thereby avoiding stress concentrations, which increases thedurability of the coupling 18. In the depicted embodiment the enlargedportion comprises an annular notch that is part of the tapered recess.It should be appreciated that in alternative embodiments the enlargedportion (e.g., notch) can be part of the tapered protrusion or both apart of the tapered recess and the tapered protrusion. It should also beappreciated that alternative embodiment may be configured without theseenlarged portions.

In the depicted embodiment the proximal end of the coupling 18 (e.g.,adaptor) which is shown threaded to the sonde housing 14 includes atapered threaded portion configured to engage mating threads of a sondehousing to toque level in excess of 50 foot pounds. As discussed above,the distal end includes a tapered portion between a first unthreadedportion and a second unthreaded portion. The first and second unthreadedportions include a constant maximum cross-sectional dimension. Asdiscussed above, the coupling includes a stop that engages an end faceof the first member to prevent full engagement of the threads (i.e.,maintains the above define offset). The stop is positioned on apredetermined location on the second unthreaded portion such that itensures an offset of at least 0.030 inches between the peaks on thethreads of the tapered threaded portion with the valleys on threads thatthe taper threaded portion is configured to engage. In the depictedembodiment the pitch diameter between the threaded portions on the firstand second members are offset by at least 0.030 inches.

The present disclosure also provides a method of connecting a drill toolto a drill rod. The method includes the steps of: contacting threadslocated at a proximate end of a drill tool member with threads locatedat a distal end of a drill rod member; threading the drill tool memberto the drill rod member by relatively rotating the drill rod member andthe drill tool member; and aligning structural features on an externalsurface of the drill tool member with structural features on an externalsurface of the drill rod member. In the depicted embodiment the step ofaligning the structural features includes counter rotating the drill rodassembly relative to the drill tool between one to ninety degrees.

The method further includes the step of sliding a collar over a portionof the drill tool member and drill rod member, wherein the collar isconfigured to engage the structural features on the external surface ofthe drill tool member and drill rod member thereby preventing relativerotation between the drill tool member and the drill string member.

In the depicted embodiment the step of threading the drill tool memberto the drill rod member simultaneously inserts a boss on the distal endof the drill tool member with an aperture on the drill rod member andinserts a boss on the proximal end of the drill tool member with anaperture on a distal end of the drill rod member. The method alsoincludes the step of maintaining at least 0.030 inch (0.76 millimeters)offset between a peak of the threads located on the proximate end of thedrill tool member and a valley of the threads located at a distal end ofthe drill rod member at least when structural features on the externalsurface of the drill tool member are aligned with the structuralfeatures on the external surface of the drill rod member. In thedepicted embodiment the pitch diameter between the threads on the drilltool and mating threads on the drill rod are offset by at least 0.030inches.

In the depicted embodiment the threading step is accomplished byrotating the drill tool member while holding the drill rod memberstationary. It should be appreciated that alternatively the drill rodcould be rotated while the drill tool is held stationary. In thedepicted embodiment, the threading step includes relatively rotating thedrill rod member and drill tool member between one to blur fullrevolutions. In alternative embodiments the threading step may includemore or fewer revolutions.

In the depicted embodiment the toque needed to unthread the drill rodassembly from the drill tool assembly is less than 50 foot pounds. Thestep of threading the drill tool assembly to the drill rod assemblyincludes rotating the drill tool member until a portion of the drilltool member (e.g., annular shoulder) abuts a portion of the drill rodmember (e.g., end face) and limits further rotation. In the depictedembodiment at least 0.030 inches offset is maintained when the portionof the drill tool assembly abuts the portion of the drill stringassembly. The at least 0.030 inches offset is maintained even if as muchas 50 foot pounds of torque are applied to the connection between thedrill rod member and drill tool member during the threading step.

In the depicted embodiment the boss on the distal end of the drill toolincludes a maximum cross-sectional dimension that is within 0.0015 to0.03 inches (0.038-0.76 millimeters) of a maximum cross-sectionaldimension of the aperture of the drill rod assembly.

Referring to FIG. 10, an alternative embodiment is shown. The depictedembodiment is similar to the above-described embodiment, however, thethreads on the tapered protrusion and aperture are removed. Instead,pins 100, 102 secure the tapered protrusion within the tapered apertureand resist tension forces between the adapter 18 and the starter rod 12.The pins 100, 102 extend through a portion of the distal end 28 of thestarter rod and driven end 46 of the adapter 18. The collar 26 slidesover the end of the pins and retains them in place.

Referring to FIGS. 11-13, another alternative embodiment is shown. Inthe depicted embodiment the tapered aperture 124 and protrusion 126 arenot threaded. Instead, the tapered protrusion 126 includes grooves 106,108, 110 that engage pins 112, 114, 116, 118, 120, 122, which are retainin pin receiving apertures that extend through a portion of the taperedaperture 124. The above described pin configuration secures the taperedaperture 124 to the protrusion 126 against tension forces applied to theconnection during operation (e.g., as the drill string is pulled backthrough the hole). In the depicted embodiment the pins can be removedafter removal of the collar 26 via driving a punch through smallerapertures that extend to the back side of the pin receiving apertures.It should be appreciated that although the tapered aperture andprotrusion are shown with a gradual taper they could alternative have astepped profile or the taper could be non-linear.

Referring to FIG. 14, another alternative embodiment is shown. In thedepicted embodiment the tapered protrusion 130 includes a spiral groove132 that is configured to mate with locking pins similar to those shownin FIGS. 11-13, which are retained in pin receiving apertures thatextend through a portion of the tapered aperture 124 in a manner tointersect the spiral groove. In this embodiment the groove 131 acts as asingle enlarged thread member that secures the tapered aperture andtapered protrusion together. This configuration provides a quickconnection and disconnection between the tapered protrusion and taperedaperture. The locking pins that mate with the spiral grooves on thetapered aperture and the receiving apertures in the aperture 124 resisttension forces applied to the connection. The collar 26 prevents thetapered protrusion from rotating relative to the tapered aperture.

It should be appreciate that many more alternative embodiments arepossible. For example, although the embodiment shown in FIGS. 10-14 areshown to include annular stress relief zone recess into the taperedprotrusion similar to those described above with reference to FIGS. 7and 8 (portions 66 and 67). Some alternative embodiment do not includestress relieve zones.

The above specification, examples and data provide a completedescription of the manufacture and use of the composition of theinvention. Since many embodiments of the invention can be made withoutdeparting from the spirit and scope of the invention, the inventionresides in the claims hereinafter appended.

The invention claimed is:
 1. A threaded interface for using inconnecting a removable down hole tool to a drill string, the threadedinterface comprising: a down hole end portion configured to interfacewith the removable down hole tool assembly; an up hole end portionopposed to the down hole end portion, the up hole end portion beingconfigured to interface with the drill string as part of a low torquecoupling, the up hole end portion including: a non-threaded non-taperedfirst cylindrical shaped portion having a first outer diameter; anon-threaded second non-tapered cylindrical shaped portion having asecond outer diameter that is larger than the first diameter; a threadedtapered section that extends between the first cylindrical shapedportion and the second cylindrical shaped portion, the threaded taperedsection including threads thereon; an annular stress relief notchproviding a transition between the threaded tapered section and one ofthe first and second cylindrical section; and wherein the threads on thethreaded tapered section are asymmetric, wherein a distance betweenadjacent valleys is 1.25 to three times greater than the height of thethread as defined by a radial distance between a peak and a valley. 2.The threaded interface of claim 1, wherein the first cylindricalsection, the second cylindrical section and the threaded tapered sectionare defined by an exterior of a male connection structure.
 3. Thethreaded interface of claim 2, wherein the annular stress relief notchis provided between the threaded tapered section and the secondcylindrical section.
 4. The threaded interface of claim 3, whereinanother annular notch is defined by the male connection structure at anintermediate location along a length of the first cylindrical section.5. The threaded interface of claim 4, wherein the male connectionstructure is a first male connection structure provided at a first endof an adapter body, wherein the adapter body has a second end defining asecond male connection structure, wherein the second male connectionstructure defines a tapered threaded section having major and minorouter diameters that are respectively larger than corresponding majorand minor outer diameters of the threaded tapered section of the firstmale connection structure, wherein the adapter body defines anintermediate region between the first and second male connectionstructures, and wherein a plurality of wrench flats are provided at theintermediate region.
 6. The threaded interface of claim 1, wherein thefirst cylindrical section, the second cylindrical section and thethreaded tapered section are defined by an interior of a femaleconnection structure.
 7. The threaded interface of claim 6, wherein theannular stress relief notch is provided between the threaded taperedsection and the first cylindrical section.
 8. The threaded interface ofclaim 7, wherein the female connection structure is provided at an endof a starter rod.
 9. An adapter for connecting a down hole tool to adrill string, the adapter comprising: a down hole end portion configuredto interface with a removable down hole tool assembly; an up hole endportion opposed to the down hole end portion, the up hole end portionbeing configured to interface with a drill string as part of a lowtorque coupling, the up hole end portion including: a first end having afirst land configured as a non-tapered cylindrical section of a firstouter diameter; a second end having a second land configured as anon-tapered cylindrical section of a second outer diameter, larger thanthe first outer diameter; a conical portion between the first end andthe second end having a threaded portion with threads thereon and astress relief zone adjacent the second land; and wherein the threads onthe threaded portion are asymmetric, wherein a distance between adjacentvalleys is 1.25 to three times greater than the height of the thread asdefined by a radial distance between a peak and a valley.
 10. Theadapter of claim 9, wherein the stress relief zone includes an annularnotch located between the second land and the conical portion.
 11. Acoupling for connecting a sonde housing to a pilot drill rod, thecoupling comprising: a down hole end portion configured to interfacewith the sonde housing, the down hole end including a taperedprotrusion; an up hole end portion opposed to the down hole end portion,the up hole end portion being configured to interface with the pilotdrill rod as part of a low torque coupling, the up hole end portionincluding: a first end portion including a threaded tapered portionpositioned between a first unthreaded portion and a second unthreadedportion; an annular stress relief notch providing a transition betweenthe threaded tapered portion and one of the first and second unthreadedportions; wherein the first unthreaded portion of the first end portionhas a non-tapered cylindrical shape; wherein the second unthreadedportion of the first end portion has a non-tapered cylindrical shape andhas a larger outer diameter than the first unthreaded portion; andwherein threads on the tapered threaded portion are asymmetric and atleast some threads have a width-to-height ratio of between 1.25 to 3.0.12. The coupling of claim 11, wherein variations in the diameter of thefirst unthreaded portion are less than 0.0015 inches and variations inthe diameter of the second unthreaded portion are less than 0.0015inches.
 13. The coupling of claim 11, wherein threads on the taperedthreaded portion are configured to engage threads on a mating membersuch that relatively rotating the tapered threaded portion and themating member connects the tapered threaded portion to the matingmember.
 14. The coupling of claim 13, wherein threads on the taperedthreaded portion are configured to engage threads on a mating membersuch that the pitch diameter between the threads on the tapered threadedportion and threads on the mating member is offset by at least 0.030inches (0.76 millimeters).
 15. The coupling of claim 11, wherein theannular stress relief notch is provided between the threaded taperedportion and the second unthreaded portion.
 16. The coupling of claim 11,wherein threads on the threaded tapered portion are configured to engagethreads on a mating member such that the pitch diameter between thethreads on the threaded tapered portion and threads on the mating memberis offset by at least 0.030 inches (0.76 millimeters).